The best replacement for iwatch is pebble.

The best alternatives to iwatch are rated as following:
★★★★★  pebble
★★★★★  galaxy gear
★★★★  google glass
★★★★  moto 360
★★★  android wear
★★★  sony smartwatch
★★★  galaxy watch
★★  samsung watch
★★  smartwatch
★★  pebble steel
  samsung gear

Your alternative for iwatch is not listed? Suggest!
Speaking about iwatch, one probably shouldn't forget about iphone 6.

Other search terms related to iwatch and their ratings are:
★★★★★ iphone 6
You have in mind a companion for iwatch and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of iwatch in all years. Click on graph for more.
iwatch
pebble
galaxy gear